1. Field of the Invention
The present invention relates to an inner rotor type brushless motor which has, for example, a rotor and a stator.
2. Description of Related Art
Generally, an inner rotor type brushless motor has a stator core fitted into and fixed to a stator case and a rotor rotatably provided with respect to the stator core, and includes permanent magnets at an outer peripheral portion thereof. This stator core includes a plurality of teeth which project radially inward. A coil is wound around these teeth. As electric current flows into the coil, an attractive or repulsive force is generated between the rotor and the stator to rotate the rotor.
Among this kind of stator, there is one which includes a plurality of teeth fixed at the internal diameter side of a cylindrical yoke portion, and a coil bobbin coupling body in which a plurality of coil bobbins around which a coil is wound are coupled together, and in which this coil bobbin coupling body is mounted on the teeth (for example, refer to Japanese Patent No. 3190511). Further, there is one in which a dovetail groove is formed at an inner peripheral surface of a yoke portion formed in a tubular shape, and a split tooth including a projection fitted into the dovetail groove is mounted on a coil bobbin around which a coil is wound to form a split core, and is then fitted into the dovetail groove (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2006-296033).
Winding starting end and winding finishing end of the coil wound around the coil bobbin are drawn out to the terminals, and are electrically connected with lead wires drawn in from the outside via the terminals.
In the above-mentioned brushless motor, the coil is the place to generate heat in the motor, and there is a problem in that the generated heat is not efficiently transferred, and remains in the motor. If the motor continues to work under the condition that the generated heat remains in the motor, it causes the overheating of the motor. Here, the generated heat by the coil is transferred through, for example, the teeth, the stator, and the stator case, and finally released to the out of the motor. In this case, a butting face between the stator case and the bracket is the narrowest and thermal resistance at the butting face is high, and the coil is not cooled effectively. Therefore, if the number of turns of the coil is increased, the heating value is also increased, and there is a problem in that the rated torque can not be improved.
Therefore, the present invention has been made in view of the above-described situations, and the object of the present invention is to provide a brushless motor capable of efficiently releasing the generated heat in the motor, and improving the rated torque.